A new resource from the National Institutes of Health (NIH) explains the A1C test to diagnose type 2 diabetes and prediabetes, and to monitor blood glucose levels of people with type 1 and type 2 diabetes.

where to learn more about A1C tests in people with hemoglobin variants

A1C targets

Originally, the A1C test had been recommended only for monitoring diabetes. But in 2009, an international committee of experts convened by the American Diabetes Association, International Diabetes Federation, and European Association for the Study of Diabetes recommended expanding the use of the test to include diagnosing type 2 diabetes and prediabetes. Because the A1C test does not require fasting, experts hope more people will be checked for prediabetes and type 2 diabetes.

The standard blood glucose tests for diagnosing type 2 diabetes and prediabetes—the fasting plasma glucose test and the oral glucose tolerance test (OGTT)—measure blood glucose in a person who has not eaten anything for at least 8 hours. The OGTT also measures blood glucose 2 hours after a person drinks a glucose-containing beverage. To confirm positive results, people should return on a different day to repeat the tests. The A1C test should also be repeated to confirm a diagnosis.